It is well known to adapt the floors of vehicles (such as vans, minibuses and coaches) for the securing of furniture, seating, wheelchairs or other objects at any of a range of locations with variable position according to need. Typically this is by one or more tracks fixed onto or integrated into the vehicle floor. The tracks have an upwardly-open internal channel, usually formed using extruded aluminum, and the top opening of the channel—extending the length of the track—is defined between opposed overhanging lips or flanges.
The most popular track format (seen in FIG. 1) is “scalloped” track 6 in which the channel opening 62 is interrupted by a series of periodic enlargements, usually of a circular outline. Each lip or flange 61 has a regular series of cut-outs 64 opposed to corresponding cut-outs 64 on the opposite lip 61. Opposed cut-out pairs constitute wide parts 62W or enlargements of the track opening. Opposed straight lip edges 63 between cut-outs provide narrow parts 62N of the track opening.
Anchorage devices usable with such track have one or more slidable foot portions with a laterally-enlarged bottom part dimensioned to be insertable into the track at a wide part but which when slid along about half a track cut-out period spacing (half a step) is held captive beneath the lips at the narrower part. An intermediate-height foot part, above the lateral bottom part, is narrower so that it can slide along into the narrow track part. One or more such slidable feet anchor the device against being pulled up away from the track.
It is necessary in some manner to lock the device longitudinally in position relative to the track so that the slidable foot cannot slide from the captive position to a removal/insertion position aligned with a track cut-out. Accordingly it is usual for an anchorage device additionally to have one or more non-slidable protrusions, dimensioned to project into a cut-out but unable to slide through the narrow parts. Such non-slidable protrusion(s) may transfer operational longitudinal loads from the anchorage device to the track as well as holding the slidable foot portion(s) in the captive position.
To be able to engage/disengage both slidable feet and non-slidable protrusions with a track, the anchorage device must provide for some relative movement between them. One conventional way is by forming a non-slidable protrusion as a “plunger”, positioned about half a step out relative to the slidable foot portion(s) and movable in the device towards and away from the track so that it can be lowered into a track cut-out after the slidable foot portion has been inserted into the track and slid to the captive position. Alternatively it is known to provide a mechanism in the device to shift a slidable foot portion and a non-slidable protrusion longitudinally relative to one another in the device, changing their spacing from being in step (and thereby insertable/removable together in relation to the track) to being substantially half a step out of step (and thereby held captive).
These rail fixing systems are widely used because of their versatility and ease of use. Fixtures do not need to be slid into the track from the end, but can be inserted into it at any point along its length. One particular use of current importance is in the securing of seats, wheelchairs or related or other fittings in vehicles e.g. vehicles designed for use by elderly and/or disabled people. For example, wheelchairs are conventionally secured by a set of four restraining straps, one at each corner secured by respective anchorages to a pair of parallel floor tracks at either side of the wheelchair. Each anchorage may be attached to a simple belt or strap with a clip, karabiner or buckle, adjustable belt, retractable and/or tensionable belt on a reel or any other suitable device or fitting. Or, the two sides of a seat may be rigidly secured down to securement means provided on an anchorage device at either side of the seat, to engage a respective track. Alternatively such anchorage devices may be incorporated into a seat base or leg structure.
It is known to provide means for avoiding or reducing play or “rattle” between a device of the kind described and the track to which it is fixed. In general a tight fit of the feet in the track channel is avoided because it makes the devices hard to insert and slide into position. Also the dimensions of different tracks—the channel depth, width, and the metal thickness at the lips—can vary and this must be accommodated. Accordingly some known anchorage devices—particularly those used for rigid seat fixtures where play, shifting and rattling are especially undesirable—incorporate mechanisms for clamping or gripping against the track in the captive position. See for example GB-A-2219493 and GB-A-2315013. However such mechanisms tend to be complex in structure e.g. requiring a tall construction, or central access to a long-form anchor, or are awkward to operate, or are incompatible with systems using insertable feet in scalloped track.